The CAS Registry Mumber 1009715-73-4 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,0,0,9,7,1 and 5 respectively; the second part has 2 digits, 7 and 3 respectively. Calculate Digit Verification of CAS Registry Number 1009715-73: (9*1)+(8*0)+(7*0)+(6*9)+(5*7)+(4*1)+(3*5)+(2*7)+(1*3)=134 134 % 10 = 4 So 1009715-73-4 is a valid CAS Registry Number.